Genetic analysis of survival and fitness in turkeys with multiple-trait animal models

Abstract

Genetic parameters for production, survival, and structural fitness traits recorded in pedigreed turkey sire and dam parental lines from a nucleus breeding program were estimated with multiple-trait animal models. Survival and conformation traits were scored in binary terms of health, where 0 = died or affected, and 1 = survived or healthy. Walking ability at 20 wk was subjectively scored from 1 (poor) to 6 (excellent). Body weights and egg production displayed moderate heritability (h(2) = 0.18 to 0.35). Early survival (to 3 wk) displayed low heritability (h(2) = 0.02 and 0.04 for the dam and sire lines, respectively). Late survival (3 to 23 wk) and longevity (age at death or cull) had low to moderate heritability (h(2) = 0.12 to 0.14). Walking ability had moderate heritability (h(2) = 0.26, 0.25). Leg structure health displayed low heritability (h(2) = 0.08), as did hip structure, foot, and skin health (h(2) ≤ 0.02). Crop health displayed moderate heritability (h(2) = 0.12). Walking ability, hip and leg structures, footpad, and breast skin health had negative genetic correlations with BW (r(G) = -0.50 to -0.23). Egg production had moderate positive genetic correlation with late survival (r(G) = 0.61). Genetic correlations between early and late survival were close to zero (r(G) = 0.10 and 0.03 for the dam and sire lines, respectively). Walking ability had high positive genetic correlations with late survival, longevity, hip structure, and leg structure in both lines (r(G) = 0.51 to 0.91). These genetic parameters indicate that unchecked selection for growth could decrease survival, walking ability, and hip, leg, footpad, and skin health in turkeys. However, index selection should be effective at improving fitness, survival, and growth simultaneously in commercial turkey lines. Walking ability should be a good indicator trait for selection to improve overall late survival and hip and leg health in turkeys.

Genetic basis of leg health and its relationship with body weight in purebred turkey lines

“…The prevalence in this study is lower than the incidence of the composite trait leg structure (Quinton et al, 2011). In their study, 16.7% of the birds in a male line and 16.9% of the birds in a female line showed a form of a leg defect, though the composite trait encompasses a variety of defects including not only valgus and varus deformities.…”

“…They also found a significant gender difference with females having a better walking ability than males. At the genetic level, Quinton et al (2011) found moderate heritabilities at 0.25 to 0.26 for walking ability. Within the Aviagen Turkeys breeding program, the visual assessment of the gait has been adopted as a selection tool, whereby birds are ranked on their relative performance compared to their contemporaries.…”

“…They present a major welfare problem because they can lead to walking difficulties and, in severe cases, lameness (Bradshaw et al, 2002). The heritabilities for leg structure (a composite trait including valgus and varus deformities) in turkeys were reportedly low at 0.08 (Quinton et al, 2011). Studies in chickens have found moderate heritabilities for valgus (0.15 to 0.39, Le Bihan-Duval et al (1997)) and varus (0.21 to 0.30, Le Bihan-Duval et al (1997)), but low heritabilities for leg angle (0.09 to 0.11, Chen et al (2011)) and long bone deformities (0.04 to 0.07, Kapell et al (2012b)).…”

“…Studies tended to find a higher prevalence in females (Krautwald-Junghanns et al, 2011; Bergmann et al, 2013). Quinton et al (2011) estimated very low heritabilities of 0.01 to 0.02 for FPD, whereas studies in broiler chickens have shown a stronger genetic basis, with heritabilities ranging from 0.08 to 0.32 (Kjaer et al, 2006; Ask, 2010; Kapell et al, 2012a). …”

Indirect Genetic Effects for Survival in Domestic Chickens (Gallus gallus) Are Magnified in Crossbred Genotypes and Show a Parent-of-Origin Effect

“…Survival in livestock populations usually has low heritabilities (Dematawega and Berger 1998;Knol et al 2002;Quinton et al 2011). In laying hens, estimates of genetic parameters for survival during the productive period of group-housed individuals are, to our knowledge, limited to those of Ellen et al (2008).…”